Flaps are like air conditioning , nobody use it before it was invented , they just opened windows and sweat lol , flaps on warbirds when used properly with trim and throttle can keep your plane and all its gear flying for a long time . If you have G2 or G3 flight sims , play with the flaps , see how the plane handles , its a total luxuary on a warbird .

Even the H9 birds with there very light wing loading could benifit from flaps .
On the other hand , planes like a Pica P40 withe heavier wing loading .... well I would not be caught dead lading this type of plane without flaps , same deal with the Top Flight P40